function s1_generate_a_series_of_files(){
  for i in {1..100};
  do
    echo $i>/tmp/new_files$i; 
  done
}
function s2_list_4_files_in_long_format_about_account_and_group(){
  ls -l /etc/{passwd,shadow,group,gshadow} | sort -d
}
function s3_find_items_related_to_given_username(){
  grep -h $1 /etc/{passwd,shadow} | sort -d
}
function s4_find_items_related_to_given_group_name(){
  grep -h $1 /etc/{group,gshadow} | sort -d
}
function s5_create_groups_for_given_group_names(){
  groupadd rnd
  groupadd itoperation
}
function s6_create_users_and_set_their_group_as_required(){
  useradd  -G rnd adam && useradd -G rnd bob && useradd -G itoperation calvin && useradd -G itoperation david && useradd -G rnd edward
}
function s7_change_users_shell(){
  usermod -s /usr/bin/sh adam
  usermod -s /usr/bin/sh edward 
}
function s8_set_password_change_policy(){
  passwd -n 10 -x 60 -w 10 adam
  passwd -n 10 -x 60 -w 10 bob 
  passwd -n 10 -x 60 -w 10 davin
  passwd -n 10 -x 60 -w 10 calvin
  passwd -n 10 -x 60 -w 10 edward 
}
function s9_set_password_for_five_users(){
  usernames=("adam" "bob" "calvin" "davin" "edward")
  for i in $(seq 1 5);
  do
  echo "${!i};
  echo $(( $i-1 ));
  done
  echo "${usernames[0]}:$1" | chpasswd 
  echo "${usernames[1]}:$2" | chpasswd
  echo "${usernames[2]}:$3" | chpasswd
  echo "${usernames[3]}:$4" | chpasswd
  echo "${usernames[$(( $i-1 ))]}:$5" | chpasswd
}
function s10_lock_bobs_password(){
  sudo usermod -lock bob
}
function s11_include_adam_into_wheel_group(){
  sudo usermod -a -G wheel adam
}
function s12_change_files_pernission(){
  for i in $(seq 3 3 99);
  do
    sudo chmod 640 /tmp/new_file$i
  done
}
